This application relates generally to railway right-of-way maintenance equipment of the type used to repair and maintain railroad track. More specifically, the present invention relates to an apparatus for replacing rail ties and for handling rail tie plates during rail tie replacement.
Conventional railroad track consists of a plurality of spaced parallel wooden ties to which are each attached a pair of spaced rail tie plates. Each tie plate is configured to rest on the upper surface of the tie and includes holes for receiving spikes or screws, as well as a canted seat or a cradle formation for receiving the bottom of the steel rail. Since two rails make up a railroad track, there is a pair of spaced tie plates on each tie. Some of the spikes are used to secure the tie plate on the tie and others are used to secure the base of the rail to the tie plate cradle.
During track maintenance operations, it is common to periodically remove worn out or rotten ties. This is accomplished by first removing the spikes which hold the plates to the tie as well as to the rail. Railroad ties are typically removed and replaced using specially designed machines. Generally, the tie replacing machines roll along the railroad track and stop at a tie needing replacement. Most machines have an extending member that positions a gripping device normally relative to the track and adjacent to an end of a rail tie to remove it. The gripping device has vice-like jaws that clamp onto the end of the rail tie (other machines have a pushing mechanism which pushes the loosened tie transversely from the track). Then, the extending member extends normally away from the track, and thereby removes the tie from under the railroad track. The reverse operation is used to insert a new tie under the track.
Although these prior machines are able to remove and replace the railroad ties, the machines are subject to several disadvantages. One disadvantage is that the extending members on the prior machines are relatively unstable. On the prior machines, the extending members are attached to the railroad repair machine frame at the center of the members. In operation, each member has an inner portion that is slidingly engaged within an outer portion and telescopes away from the frame to position the gripping mechanism relative to the rail tie. The length of the fully extended member places stress at the attachment point where the end of the member meets the frame. This stress often causes the member to sag, work improperly or even break over time. Furthermore, some prior machines only had one extending member, which was attached to a pivot, in order to remove ties from the other side of a track if necessary. These machines experienced additional stress at the attachment point due to the excess movement and vibration on the extending member.
More recently developed machines include two extending members, one on each side of the machine that are mounted along the same axis. A main support member is situated in the middle of the machine frame and contains the two extending members which are slidingly engaged with each other. This innermost member extends in an opposite direction from the next outer member. In operation, one extending member slides outward within the main support member, and away from the machine frame, towards the location of the rail tie.
The dual in-line extending member design increases efficiency and overcomes the stress experienced by the single pivoting extending member design. These machines can remove a rail tie from either side of a track without pivoting, however stress problems still occur when the extending member is completely extended away from the frame. The full extension places most of the weight of the extending member on the minimal contact point between the extending member and the main support member. Stress is created on the contact point between the main support member and extending member, and failure results.
As the tie is extracted, the loosened tie plates either fall into the rail bed or ballast, or are retained on the removed tie. Conventional practice is to manually remove the plates and throw them off to the side of the ballast so that they do not interfere with the replacement of the new tie. Once the new tie is inserted under the raised track, the plates must be reinserted in the appropriate position to support the rail and for re-spiking.
To avoid on the job injuries, especially those involved with handling tie plates, which typically weigh approximately 18-40 pounds and are heavy to manipulate, railways have attempted to mechanize the tie replacement and plate placement process as much as possible. One attempt has been to provide a mechanism which grips the plates and secures them to the rail as the tie is removed from beneath the plates. This system has not been widely accepted by the railroads because of its relatively complicated mechanism, and because in many instances the insertion of the new tie will cause particles of railway ballast to be retained on top of the tie and interfere with the repositioning of the tie plates. These conventional mechanisms have no way to remove unwanted ballast particles from the top surface of the tie.
Another drawback of conventional mechanized plate placement devices is that their speed is relatively slow and they cannot keep up with the other operations of the rail maintenance gang. Using manual removal and placement of tie plates, the tie replacement process typically operates at a rate of about 15 ties per minute. Conventional mechanized plate removal devices operate in the range of 3 to 5 ties per minute. At this point, this rate of production is unacceptable to the railroads.
Thus, there is a need for improved rail maintenance machinery which addresses the above-listed drawbacks by synchronizing the operations of tie extraction and plate handling. In addition, there is a need for an improved tie plate handling apparatus which addresses the problem of tie plates getting in the way of the tie extraction process. Another need in the industry is an improved plate handling system which reduces the manual handling of plates during the tie replacement process.
The above-listed goals are met or exceeded by the present combined tie extractor and plate remover, which features the ability to grasp tie plates independently of the tie extraction procedure. In this manner, the tie plates do not interfere with the extraction and/or subsequent insertion of ties. Also, the tie plate remover assembly is preferably movable relative to the main machine frame, which allows the removed tie plates to be released remotely from the location of the tie extraction. In addition, when two non-axially aligned tie gripping extending members are provided on the frame, the movable tie plate remover assembly may be selectively movable to reference points associated with each of the extending members for operation on either side of the frame or either rail.
More specifically, a combined tie extractor and plate remover for railroad track maintenance includes a frame configured for movement along the track and having a first side corresponding to a first side of the track and a second side corresponding to a second side of the track, each side of the track having a corresponding rail. A rail lifting apparatus associated with the frame is configured for lifting a selected one of the first and second rails away from the track. A plate remover assembly associated with the frame is configured for grasping and removing tie plates associated with each side of the track from a selected tie. At least one tie extracting assembly is disposed on the frame for extracting the gripped tie transversely relative to the track in conjunction with the removal of the tie plates.
In another embodiment, a method for extracting ties and removing plates from a railroad track having a first and a second rail, includes gripping both tie plates located upon a tie to be extracted using a tie plate gripping assembly, lifting one or both of the rails of the track at a selected location of a tie extraction, pulling the tie plates away from the tie, grasping an end of the tie to be extracted adjacent the location where the rail is lifted, the grasping being performed by a tie gripping and extraction assembly, pulling the grasped tie transversely relative to said track from the point where the rail was lifted, and releasing the gripped plates.